The present invention relates to an apparatus for applying silicone oil onto the surface of the fixing roll of a plain paper copying (PPC) machine.
In the fixing mechanism of a PPC machine, paper bearing transferred toner particles is passed between a heated fixing roll and compression roll made of rubber or other elastic material under pressure at a predetermined temperature in order to fix the toner image. In this mechanism, there is a tendency for the paper bearing toner particles to become wound around the fixing roll or elastic compression roll thereby preventing complete printing or jamming the machine. To avoid these problems, various techniques have been proposed.
All conventional types of fixing mechanisms apply a coating of a release agent onto the surface of the fixing roll and compression roll. It is however very difficult to apply a release agent coating uniformly and in the right amount. If the amount is too large, the agent forms a blotch on the paper or discolors it. At the same time, rapid consumption of the agent requires its frequent and uneconomical refilling. Furthermore, excess release agent coagulated on the roll surface can cause unexpected trouble with the machine. If too small an amount of the release agent is applied, the releasability of the roll surface from paper is unavoidably reduced leading to the problem of the paper being wound around the roll. Typical release agents are silicone oil and other heat-resistant oils.
Conventional applicators for the release agent include the following:
(1) An applicator wherein the fixing roll or compression roll is partially immersed in the release agent and excess release agent is scraped off the roll with a doctor blade or other suitable device; and
(2) An applicator wherein the release agent is applied to an intermediate roll before being transferred onto the fixing roll. This type of applicator is shown in accompanying FIG. 3 wherein reference numeral 11 designates a release agent supply jig, 12 an intermediate roll, 14 the fixing roll (heating roll), 15 an elastic compression roll, and 16 the copy paper.
The first and second applicators cannot apply a uniform coating of release agent and tend to apply an excessive amount of the agent so that the problems described above arise. In addition, they not only consume the agent too rapidly but also require a large installation space.